This application claims priority under 35 USC 119 to German Patent Application No. 10 2006 027 915.8 filed on Jun. 17 2006, the contents of which are herein incorporated by reference.
1. Field of the Invention
The method relates to the production of Mg(OH)2 nanoparticles, in other words particles having a diameter ≦100 nm. These Mg(OH)2 nanoparticles can be converted into MgO nanoparticles by means of calcination.
2. The Prior Art
Mg(OH)2 nanoparticles and MgO nanoparticles are finding increasing importance in technical applications, such as, for example, as a catalyst material, in the modification or finishing of material surfaces, such as, for example for the purpose of surface hardening or UV stabilization. Nano-scale Mg(OH)2 particles and MgO particles are furthermore used in the modification of plastics/polymers in connection with flame protection. Another area of use relates to functionalized electrodes and so-called hopping processes.
Several methods are known for the production of nano-scale particles, and especially of MgO particles and Mg(OH)2 particles, respectively.
A common method represents the wet grinding of MgO or Mg(OH)2. Disadvantages of this method are an inefficient use of energy as well as a broad particle size distribution. Another disadvantage lies in the fact that the synthesized nanoparticles must be stabilized to prevent re-agglomeration, by means of adding an additive.
The synthesis of MgO nanoparticles or Mg(OH)2 nanoparticles has been essentially based on gas phase methods until now. In German Patent No. DE 101 09 892 A1, a pyrolysis method, proceeding from MgCl2, for the production of nano-scale MgO having a monomodal particle size distribution is described. Since gas phase methods have the result of the formation of not fully saturated, i.e. unprotected solid body surfaces, it can fundamentally be assumed that an agglomeration of the MgO particles will occur after their synthesis.
German Patent No. DE 102 54 567 A1 discloses a production method for ZSO4 nanoparticles (Z=Mg, Ca, Sr, or Ba, or binary mixtures of the same) in coordinating solvents such as, for example, ethylene glycol or other polyethylene glycols. The nanoparticles synthesized according to this method have a diameter of 0.5 nm to 50 nm and are characterized by a narrow particle size distribution.
This production method cannot be transferred to the production of Mg(OH)2 nanoparticles or MgO nanoparticles, respectively, because of the high basicity of Mg(OH)2 and MgO, respectively ([OH−]>10−4 mol 1−l). Because of the high concentration of hydroxide ions [OH−], decomposition/polymerization of the polyol component is to be expected, and this prevents a targeted synthesis of nanoparticles.